The present invention generally relates to a heater assembly and, more particularly, to a vacuum insulated quartz tube heater assembly for heating fluids and objects.
The use of quartz glass to encase a heater element is known in the art, since quartz glass has the ability to sustain the high temperatures that are generated by the heater, while the quartz glass is relatively chemically inactive. Typically, electrically resistive wires, ribbons, and coils have been used as heater elements within quartz heaters to generate the required heat.
Recently, conductive metal oxide films (coatings) have been employed as heating elements, where the films are generally disposed on glass. One of the methods for depositing the films has been to spray coat the films onto the glass. More recently, the depositing of the coatings has improved, for example, through the use of chemical vapor deposition (CVD).
An application of quartz glass that would benefit from the employment of the use of the conductive coating as a heating element would be a quartz glass heater for the heating of a fluid or other material as the fluid would flow through the quartz glass heater. In such a heater, the heating element would need to elevate the fluid temperature as the fluid would pass through the heater.
If a quartz glass heater, using a thin film conductive coating, could be constructed it would be an improvement over the conventional heater element, since the conventional wire, ribbon, or coil elements are more costly, more bulky, and add weight to the heater assembly.
However, achieving such a deposition on curved quartz glass has proven to be difficult. This is due to the fact that the conductive coating must be uniformly disposed upon the quartz glass in such a manner as to properly electrically section off the conductive coating, while achieving a necessary resistive load for the desired output power.
In addition, expanding the adoption of this technology is hampered by the complexity of safely, reliably, and cost effectively combining glass and electricity. Because of the high temperatures that are generated by the heater, the chemical reactivity of the parts of the heater, along with the atmosphere within the heater, become important factors affecting the reliability of the heating assembly.
If the parts and/or atmosphere within the heater assembly are not properly chosen the high heat will cause the materials and the atmosphere to interact and lose their functionality, which will shorten the life of the heater assembly. In the past, conventional quartz glass heating elements have been disposed within a vacuum. As a result, the quartz glass, which has a low chemical reactivity, the vacuum/atmosphere within the quartz heater, and the various parts within conventional quartz glass heaters would have to be properly chosen in order to provide better reliability for the heater assembly.
Thus, those skilled in the art continue to seek a solution to the problem of how to provide a better vacuum insulated quartz glass heater assembly.